1998-06-06 04:00:00 PDT Salt Lake City -- Baptist missionaries Fred Tiedemann and Henry Deneen brought their Bibles and their beliefs into Temple Square this week, the sacred heart of the Mormon Church and the site of a weekend showdown between American evangelicals and one of the world's fastest-growing faiths.

To outsiders, the Southern Baptists -- who are arriving by the planeload for a national convention in Salt Lake City -- and the Church of Jesus Christ of Latter-day Saints seem to have a lot in common. They are both politically conservative, morally pious and hungry for converts. They both praise Jesus, condemn alcohol and fight gay rights.

But when they start talking about doctrine, "I love you, brother" quickly turns into "You'll burn in hell, sister."

"We tell them that the Book of Revelation says don't add or subtract to this book," said Deneen, a student at Golden Gate Baptist Theological Seminary in Marin County. "It's pretty hard to believe that and the Book of Mormon."

At his church office across the street from the six-spired Mormon Temple, Alexander Morrison, president of the Latter-day Saints in Northern Utah, is not impressed with the Baptist missionary's biblical knowledge.

"That is such a hackneyed argument and unbelievably naive," said Morrison, leaning back in his chair and fingering his suspenders.

"Anybody who knows anything about how the Bible was put together knows that when John wrote those words, there was no such thing as the Bible," he added. "Christians down to this day do not agree on what books should be in the Bible. Catholics have more books than Protestants."

Deneen and Tiedemann, both of whom came to the Marin seminary from South Carolina, have been in Salt Lake City for four days, learning about Mormonism and how to convert the Latter-day Saints to evangelical Christianity.

Most of the Baptists' door-to-door crusade will take place today. Called "Crossover Salt Lake City," the $600,000-evangelical blitz also includes TV and radio spots and a direct mail campaign to reach 400,000 homes in the region. The annual Baptist convention, which is being held at the Salt Palace Convention Center, begins Tuesday and concludes Thursday.

Neither Morrison nor other Mormon leaders seem very concerned that some 20,000 Southern Baptists are coming to town over the next week, preceded by an advance team that has been spreading the word that Mormons are a polytheistic "counterfeit Christian movement" promulgating heresy and offering only false hope for eternal salvation.

"Let 'em come," said Morrison. "They come. They go. It's fine. It's kinda like water off a duck's back."

Morrison has reason to be smug. Membership in his church is exploding around the world. Despite increasing religious diversity closer to home, Utah remains about 70 percent Mormon.

Meanwhile, there are only about 15,000 Southern Baptists in the combined states of Utah and Idaho -- which is about the size of a large Baptist church in Dallas.

Despite their doctrinal differences, the Baptists agree that the Latter-day Saints can teach them something about winning converts.

Proselytizing has been a Mormon mandate ever since Joseph Smith Jr., the founder of the Latter-day Saints, published the Book of Mormon in 1830, saying the text was based on ancient golden plates revealed to him by an angel named Moroni in upstate New York.

Today, the church boasts a dedicated force of 58,000 young missionaries seeking converts all over the world -- from the streets of San Francisco to the most remote African villages.

In just the past 20 years, the worldwide Mormon church has more than doubled in size, from 4.6 million members in 1980 to around 10 million today.

That growth does not sit well with the leaders of the 16 million-member Southern Baptist Convention, which is also known for its missionary force.

"We're growing through all the Southern states," said Mormon church spokesman Michael Otterson, who said the Mormons are planning no special "counterattack" in that Southern Baptist stronghold.

"Joseph Smith does not bear any of the marks of a genuinely moral or genuinely righteous man," Roberts said. "The guy had 33 wives. He was driven out of Ohio for starting a bank that had no collateral. He was arrested as a young man for practicing occultism. We believe the Book of Mormon is a total fabrication."

Roberts, author of a new book entitled "Mormonism Unmasked," cites the research of excommunicated Mormon historian D. Michael Quinn, who showed that "Joseph Smith's religion was not so much Christianity but an accumulation of folklore, superstition, occultism of the time and Freemasonic thought."

To appear more like mainstream Christianity, Roberts said, the Mormons have been playing down their belief that God was once a man, and that man can become like God through "eternal progression."

In an interview last year with The Chronicle, Gordon Hinckley, the president and prophet of the Latter-day Saints, shocked many Mormons when he was asked if Mormons really believe God was once a man. Hinckley replied, "I wouldn't say that. . . . That gets into some deep theology we don't know very much about."

Roberts also said the Mormons open themselves up to the charge that they are, theologically speaking, a "cult" because they believe their church is the only true expression of Christianity.

"We believe the gospel of Christ was restored through the Prophet Joseph Smith," Morrison said. "And that it was a restoration of truth that had been lost as the church adapted to Hellenism, paganism and other 'isms' that came along."

Morrison said he hoped that the Baptists "will go away with more information about the church than when they came."

Referring to 19th century persecution of the Mormons, he said, "We've been abused for a long time."

"We're not made out of sugar candy," Morrison added with a smile. "We'll survive."